The present invention relates to a rotary character-carrying member and the selector device therefor for a print unit of typing machines and in particular electronic typewriters, comprising a motor shaft which can be positioned in a plurality of angular positions and in which the character-carrying member can be removably connected to the motor shaft and is provided with identification elements disposed in a coded fashion along a circular ring thereon.
Typewriters which use character-carrying members with identification elements are generally provided with a detection or recognition circuit which, in an initialization phase of the machine, provides for rotary movement of the character-carrying member and for recognition of some characteristic parameters of the character-carrying member, thus simplifying use of the machine.
An arrangement of the above-described type is known in which the character-carrying member is of the daisywheel type, in which the motor shaft is rotated by a stepping motor and in which the circuit for recognition of the identification elements detects the coded position of the identification elements, recognises a particular reference position of the character-carrying member and activates the motor for a number of steps such as to position the character-carrying daisywheel in its zero position. That arrangement requires a recognition circuit which has a high degree of angular resolution and positioning of the identification elements which is so accurate as to discriminate the reference position with a maximum error that is less than half the angular step of the character-carrying petals. That is necessary in order to avoid the zero position of the daisywheel being associated with a different petal from the predetermined petal. The character-carrying daisywheel and the recognition circuit are therefore rather expensive.